Quantum simulation with superconducting qubit arrays.

Superconducting circuits have emerged as a strong candidate for building working universal quantum computers, but a range of difficult challenges still remain to be solved before this dream is finally realized. Besides commercially relevant applications, the same circuits used for quantum computing can also be employed to implement accurate simulations of many-body quantum physics. This scientific application places less stringent criteria on the fidelity of control operations in the circuits, and hence is likely to be realized as one of the earliest real-world applications.

This project will build on the recent development of a new architecture for quantum computing in our group based on coaxial circuit elements and out-of-plane control. We have demonstrated the architecture at the two-qubit level, including full two-qubit quantum logic at close to state-of-the-art (99.9% and 98% fidelities for one and two-qubit gate fidelities respectively) [1]. Recent as-yet unpublished work shows that we can reach world record coherence and fidelities in 4-qubit circuits using a new innovation that will enable us to scale to large 2D arrays of qubits [2].

The project will initially involve design, simulation, fabrication and measurement of multi-qubit circuits designed to implement Hamiltonians of interest in condensed matter physics, such as the Bose- and Fermi-Hubbard models, in particular with a view to scaling up the circuits to 2D (and potentially further). The project will then move on to demonstrate quantum simulations at an intermediate scale of 16+ qubits, where 2D effects become apparent, enabling observation of phenomena that occur in the bulk and at the edges of lattices in these Hamiltonians.

EPSRC Priority area: 21st century products: Quantum technologies: Quantum computers. This project focuses on demonstrating an important scientific application of quantum computers, the implementation of quantum physics simulation, which will develop into a valuable new tool for Physics research.

[1] Patterson et al., PR Applied 12, 064013 (2019)
[2] Spring et al., PR Applied 14, 024061 (2020)